Yeast Wranglers

When Josef Groll was preparing to brew in the Citizens’ Brewery, Mestansky Pivovar in the southwest region of Bohemia, his mind was focused on creating a bright, golden beer – one that would mark the beginning of a modern era. It was 1842 and Groll was challenged with hitting that proverbial home run with a style of beer that would have soft round notes, fresh-bread maltiness, firm bitterness, and the golden clarity of a yellow diamond.

He had some advantages. An architect named Stelzer built an ultra-modern brewery on sandstone, and appointed him Master Brewer of this new facility. The regional water was soft and minerally. Malted barley would progress through a triple-decoction mash routine, and choice Czech Saaz hops were to be added three times throughout the operation. And what about yeast?

Legends abound that one of Groll’s long-time loyalists, a monk, wrangled yeast from a Bavarian brewery for his use. Zythophile Martyn Cornell, however, debates that little story. He prefers to believe that Groll himself may have taken yeast from his own family brewery, Grollschen Brauerei, in Vilshofen an der Donau in Lower Bavaria.

I have to agree with Cornell. It was not until 1857 that Louis Pasteur explained the fermentation process and the role yeast played in the transformation of wort into beer. Prior to that time, wort was converted to an alcoholic beverage because “God is Good.” The probability of someone smuggling yeast in ideal conditions for use in a new beer seems preposterous. Groll knew he needed a “starter,” and he likely got it from a familiar source.

These days, yeast is a coveted commodity. Industrial commercial brewers such as AB-InBev or MillerCoors claim to use the same strain in their brewing today as was brought from Europe by their founding fathers. In order to keep the flavors fresh and consistent, great pains are taken to isolate a few single cells of this microscopic fungus, save them as pure cultures on slants; then, freeze them in a sterile medium to protect them from contaminants.

But you don’t have to be a macro-brewer to cultivate yeast. Many small craft brewers wrangle yeast from bottle-conditioned or cask-conditioned beers in which the yeast are still alive and doing their chomping. These beers are the unpasteurized ones, and may be dosed up with an additional hit of yeast after primary fermentation. A sterile swab is enough to swipe a beer sample onto a slide. The yeast is easily identified – usually in clusters – and it is up to you to select a healthy specimen. Healthy is not characterized by being over-sized one or the tiniest ones. This is where being Average Joe is the best of the best.

Your choice yeast can be retrieved with an inoculation loop. The yeast is then placed in a sugar-rich, commercially available starter and allowed to propagate at will. Yeast expert Dr. Maribeth Raines-Casselman has demonstrated, for brewers across the country, that the special flavors that make distinctive brews are developed from the yeast. She and her husband are both homebrewers, and have made beers that taste like those from which they retrieved yeast.

Not every craft brewery or homebrewer is set-up for this sort of thing, but if your living room is filled with microscopes, agar plates, stir plates, sterile swabs, an autoclave, and a glove box (clean chamber) like mine is, you may have what it takes to rustle up some yeast. A dedicated freezer helps, too.

Belgian brewers of the Senne Valley in Belgium tend to brew in the cooler weather, using the natural yeast in the air to propagate their beer. These wild yeasts are native to the region and produce beers that are earthy, tart, fruity and complex. Urbain Coutteau of De Struise Brouwers retrieved a yeast strain from a plum that his child picked while on vacation in 2003. This wild yeast was so effective, that it is used in all of the de Struise beers today.